1. Field of the Invention
The invention relates to a power supply system for supplying power to an electronic apparatus, more particularly to a power supply system that can ensure efficient utilization of battery resources of an electronic apparatus.
2. Description of the Related Art
A conventional power supply system for supplying power to a load of a notebook computer includes a rechargeable battery unit, a switch unit coupled to the rechargeable battery unit and the load, and a detector coupled to the rechargeable battery unit and the switch unit. The load generally requires a minimum operating voltage of 3.0 Volts. The rechargeable battery unit, when fully charged, generally has a maximum voltage output of 4.2 Volts. The detector detects a remaining capacity of the rechargeable battery unit, and compares the remaining capacity of the rechargeable battery unit with a predetermined reference value. The remaining capacity of the rechargeable battery unit is derived from a detected voltage output of the rechargeable battery unit. The predetermined reference value, which is the function of a minimum operating voltage required by the load, is typically set at 3.4 Volts. When the remaining capacity of the rechargeable battery unit is higher than the predetermined reference value, the detector enables the switch unit so as to maintain electrical connection between the rechargeable battery unit and the load such that the rechargeable battery unit supplies the power to the load. On the other hand, when the remaining capacity of the rechargeable battery unit is lower than the predetermined reference value, a corresponding warning message is provided. A predetermined time period after the warning message is provided, the detector enables the switch unit so as to break electrical connection between the rechargeable battery unit and the load such that the power supplied by the rechargeable battery unit to the load is suppressed.
The aforesaid conventional power supply system is disadvantageous in that the predetermined reference value is set to a voltage that is typically 10–15% higher than the minimum operating voltage of the load. Therefore, the power supplied to the load is suppressed way ahead of time as a precautionary measure. However, the remaining capacity of the rechargeable battery is under-utilized.